Doctors recommend how to handle contaminated water after floods

Specialist Doctor I Bui Thi Thuy Ngan - Head of the Department of Environmental Health, School Health, Nghe An Province Center for Disease Control recommends: When floods occur, floodwaters flood everywhere, sweeping away everything on the ground such as waste from sewers, animal carcasses, manure from livestock and poultry, insects, fallen trees... causing serious pollution of water sources and the environment. Water wells are also likely to be submerged in floodwaters.

Therefore, after the flood recedes, measures must be taken to immediately treat contaminated water sources and environments to prevent the risk of infection and health effects. People need to clean water tanks, wells, water containers and use chemicals to disinfect drinking water and domestic water according to the instructions of medical staff. To treat contaminated well water, it is necessary to dredge and wash the well, clarify the well water and disinfect the well water properly.

Doctor Bui Thi Thuy Ngan guides people on how to treat domestic water during floods. Photo: Thanh Chung

About dredging and washing water wells

Everyone needs to clear all the stagnant water around the well area; remove the lid or nylon sheet covering the well mouth. Before making the water clear and disinfecting, the well must be dredged; use well water to pour over the well wall to wash away all the sand, dirt, and trash stuck on the well wall and floor.

If the well is flooded and has turbid water, it is necessary to drain the water and remove all the mud. In areas with electricity or a generator, use an electric pump to drain the water and then dredge the well. In case it cannot be dredged, choose another well to treat and share. If all the wells in the area cannot be dredged, temporary treatment measures can be applied such as drawing a few dozen liters of water into a tank, then adding alum and disinfecting. After that, the treated water can be used temporarily. When the water is used up, perform additional batches for use; wait a few days until the well water level drops and then dredge.

Cleaning the water environment after floods requires people to follow the instructions of the health sector to ensure their health. Photo: Huy Thu

In case there is no alum to clarify the water source, you can make a temporary sand filter tank with a barrel, bucket or jar with a capacity of about 20 - 30 liters of water. Punch a hole with a diameter of about 1 cm on the wall, 5 cm from the bottom of the barrel. Put some rocks or broken bricks at the bottom, put a piece of burlap on top and pour sand about 25 - 30 cm thick. Pour in well water until the water flows out clear, then use it for disinfection.

Ifflooded wellHowever, if flood water does not overflow into the well and the well water is still clear, it must still be sterilized before use. If conditions permit, the water should be drawn out and dredged. If conditions are not available, the water in the well can be sterilized immediately for temporary use; a few weeks later, the well water should be dredged.

It is important to note that flooded wells must be dredged and disinfected before they can be used. When a series of flooded wells are in need of water and there is a high demand for water but not enough manpower to treat the water, each residential area should choose a few wells to treat first so that water can be used immediately. In areas where flooding often occurs, it is necessary to prepare a small generator and a water pump to be able to treat some wells for residential areas in case of need.

With the process of clarifying well water

Due to the turbidity of flood water, people can use alum, the commonly used type is aluminum alum, with a dosage of 50g/1 cubic meter of water. If the water is very turbid, the maximum amount of alum can be up to 100g/1 cubic meter of water. Dissolve all the necessary amount of alum in a water bucket or bucket, and sprinkle the solution evenly into the bottom of the well. Lower the water bucket deep into the well, pull the bucket up strongly about 10 times, then leave it for about 30 minutes to 1 hour for the sediment to settle, then continue to disinfect.

Heavy rains caused flooding, greatly affecting people's daily life. Photo: Huy Thu

About well water disinfection

Well water contaminated by floods, in principle, after disinfection, must have an excess chlorine concentration of 0.5 mg to 1 mg per liter of water. Calculate the amount of chloramine B needed for the well based on the required concentration of 10g/1 cubic meter of water. Other chemicals such as 20% lime chloride (13g/1 cubic meter of water) or 70% lime chloride (4g/1 cubic meter of water) can also be used.

Scoop a bucket of water, mix the above chemicals into the water, make sure to stir well until dissolved. Pour the bucket of water evenly into the well. Lower the bucket of water to half the water column in the well, then pull it up and down about 10 times. Use the well water that has been used to disinfect the well, leave it for about 30 minutes, then the water source can be used.

One thing to note is that although well water has been disinfected with chloramine as above, the water must be boiled and cooled before drinking. In the absence of chemicals to disinfect well water, you should only eat and drink well water that has been boiled for 10 minutes or more and should not eat raw vegetables washed with unsterilized water.

With well water

The treatment of well water is simpler. People need to pump out all the turbid water and continue pumping for about 15 minutes to remove water that may be contaminated. Then the well water can be used. People need to pay attention to cleaning the water pump and the well floor.